1. Field of the Invention
The present invention generally relates to a fan shroud that covers an outer periphery of a cooling fan that is disposed rearwardly of a vehicle mounted heat converter such as a radiator. More specifically, the present invention relates a fan shroud for a vehicle mounted heat converter in which the cooling fan is disposed such that a portion of the cooling fan is located above a core of the heat converter.
2. Background Information
In a cooling fan for a heat converter such as a radiator mounted on a vehicle, an adequate amount of air is effectively obtained by covering a periphery of the cooling fan with a fan shroud, and also by adjusting the shape of the fan shroud. A main engine that is disposed rearwardly of the cooling fan is an obstacle with respect to the rear airflow from the fan. However, when the distance between the cooling fan and the engine or obstacle is short, a mixed airflow fan is utilized that sends the rear airflow from the fan in a diagonally rear direction in order to reduce the resistance.
Most cases in a vehicle, the fan shroud and the cooling fan are disposed rearwardly of a heat converter such as a radiator. An xe2x80x9coverlap ratio (b/a)xe2x80x9d of the blades of the cooling fan to the fan shroud is one of the important factor among factors that relate to the shape of the fan shroud in order to maximize the performance capacity of the cooling fan as possible with minimal losses. In the xe2x80x9coverlap ratio (b/a)xe2x80x9d, the dimension xe2x80x9caxe2x80x9d represents the axial depth of the fan blades of the cooling fan in the axial direction. The dimension xe2x80x9cbxe2x80x9d represents the axial dimension of a side portion of the fan blades of the cooling fan that is covered with the fan shroud. In other words, the overlap ratio is defined as the ratio of an axial dimension of the fan shroud that axially covers a portion of the fan blades relative to the overall axial depth of the fan blades
Generally, when xe2x80x9coverlap ratioxe2x80x9d is small, a reversed airflow can occur within the fan shroud. Also, suction from outside the fan shroud can occur on the downstream side of the fan blades of the cooling fan. Accordingly, the amount of the airflow may decrease through the radiator. Conversely, when a mixed airflow fan is utilized with a large overlap ratio, the overlapping portion of the fan shroud (the portion that corresponds to dimension xe2x80x9cbxe2x80x9d becomes an obstacle to the mixed airflow. Accordingly, the amount of the airflow may decrease through the radiator. Therefore, it is necessary to adjust the shape of the shroud besides increasing the overlap ratio, such that the shroud will not be an obstacle to the mixed airflow.
In view of the above, there exists a need for a fan shroud which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
It has been discovered that there has been a recent tend towards designing vehicles with lower hoods and shorter overhangs. For instance, if a front end of the hood becomes lower, the mounting position of the heat converter or radiator in the vehicle becomes lower. Accordingly, the height of the heat converter or radiator has to be shortened. Therefore, the cooling fan is disposed so as to be offset upward relative to the heat converter or radiator. Accordingly, a portion of the cooling fan is above an upper end of a core portion of the heat converter or radiator. In this case, in order to shorten the height of the fan shroud, the shape of the fan shroud at a portion that corresponds to the offset portion should be in a ring shape so as to conform to the shape of the fan. However, when the portion that corresponds to the offset portion is formed into a ring shape, the aforementioned resistance against the mixed airflow becomes substantially large, which is not preferable.
Since the cooling fan is offset upward, the flow of the cooling air from heat converter to the cooling fan is oriented in a diagonally upward direction at the offset portion. Accordingly, the resistance increases in the air flowing from heat converter to the cooling fan. In particular, in the case of a short overhung vehicle where the distance between heat converter and the cooling fan is short, this tendency increased resistance is more prevalent. The cooling air that passed through the heat converter suddenly flows upward in the vicinity of the cooling fan. As a result, there is more resistance in the offset portion. Accordingly, the amount of the airflow may decrease in this region.
An object of the present invention is to provide a fan shroud for a vehicle mounted heat converter that can effectively obtain the necessary amount of air, where a portion of the cooling fan is disposed above the core of the heat converter within the fan shroud.
According to one aspect of the present invention, a fan shroud is provided for a vehicle mounted heat converter that covers a side periphery of fan blades of a cooling fan, which is partially offset from a core portion of the heat converter when viewed from a front side of the heat converter. The fan shroud basically comprises a non-offset shroud portion disposed about a non-offset section of the fan blades, and an offset shroud portion disposed adjacent the non-offset shroud portion and disposed about an offset section of the fan blades. The non-offset shroud portion has a non-offset overlap ratio at the non-offset section of the fan blades. The non-offset overlap ratio is defined as a ratio of a first axial dimension of the non-offset shroud portion that axially covers a portion of the fan blades relative to the overall axial depth of the fan blades. The offset shroud portion has an offset overlap ratio at the offset section of the fan blades. The offset overlap ratio is defined as a ratio of a second axial dimension of the offset shroud portion that axially covers a portion of the fan blades relative to an overall axial depth of the fan blades. The offset overlap ratio at the offset shroud portion is smaller than the non-offset overlap ratio at the non-offset shroud portion. In this manner, the aforementioned object is achieved.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.